apache_request_headers—获取全部 HTTP 请求头信息 arrayapache_request_headers (void) 获取当前请求的所有请求头信息 参数 ...

If this is information that's independent of the request (that is, something used in a variety of requests) and is used to control the processing of the request, then I'm more likely to put the data ...

An example of a common request header sent to the server is If-Modified-Since. The server returns the file only if it has been changed since a certain date and time. See HTTP.